1. Field of the Invention
The present invention relates to a controller for controlling a moving object, such as an automobile, an elevator, etc. The present invention also relates to a method of controlling such a moving object, to a sensor for use in such a controller, and to the combination of a moving object and such a controller.
2. Summary of the Prior Art
In order to control a moving object, such as an automobile, elevator, etc., it is necessary to sense that movement. Existing arrangements are known in which sensors are provided for detecting at least one of: position, velocity, angular velocity, acceleration and angular acceleration. The information derived from such sensors may then be used to control the object. For example, a sensor may detect the acceleration of an object and the information thus obtained may be used to control the acceleration so as to obtain a smoothly increasing velocity.
For a human observer being carried by a moving object, position and velocity are not sensed directly, but are determined only by observing a change relative to stationary objects. However, acceleration is readily sensed. Furthermore, it is suggested in an article entitled "Development of Acceleration Sensors for Automobiles" published in the Nissan Technical Bulletin No. 23, of December 1987, that human beings are particularly sensitive to the rate of change of acceleration, i.e. the differential of acceleration. That article suggested that differential acceleration relates closely to feelings of comfort or discomfort experienced by a human being moving with the object.
In its most general aspect, the present invention proposes that the movement of a movable object be detected, and a value representing a differential of the acceleration relating to that movement be derived. Then, according to the present invention, a control signal is generated in dependence on that value, thereby to control the movable object.
Therefore, a first aspect of the present invention relates to a controller for controlling the movable object, and a method of controlling a moving object. Within this aspect of the present invention, it is possible to derive a value representing the acceleration of the object, which may be achieved by known sensors, and then to derive the differential of that value by, for example, a suitable differentiating means. However, it is preferred within the present invention that a sensor be provided which is capable of determining the differential of acceleration directly.
Therefore, according to a second aspect of the present invention, a sensor is provided with two members movable relative to each other, with one of the members carrying a magnet and the other a coil. Then, if relative movement occurs, a current may be generated which, when passed through the coil, generates a force due to the interaction of the current with the magnetic flux of the magnet. If that current is generated such that the force resists relative movement of the members, it has been found that the voltage across the coil then provides a direct measurement of the differential of acceleration.
Although such a sensor has been derived for use as a part of the controller of the first aspect of the present invention, it is an independent aspect of the present invention.
In such a sensor, one of the members is preferably a pendulum mounted via a pivot axis on the other member. Whilst it is possible for such a pendulum to have two degrees of freedom of movement, so that the differential of acceleration can be derived in more than one axis, the processing circuitry then necessary is complex, and it is preferable that the movement of the pendulum is limited to a single plane. If the differential of the acceleration is needed in more than one direction, then a plurality of such sensors may be provided.
Furthermore, although it is normally easier to mount the coil on the moving part, e.g. the pendulum, it is also possible to mount the magnet thereon, with the coil being mounted on the other member.
Although the present invention proposes that a control signal be generated which is related to the differential of acceleration, it is not limited to controllers in which the differential of acceleration is the only factor used for controlling the moving object. Thus, for example, it is possible to derive acceleration and/or velocity and/or position information relating to the movement of the movable object, and use such information, together with the differential of acceleration, to control the object. Furthermore, the present invention is not limited to linear acceleration, and the differential thereof, but may also be applied to angular acceleration and the differential thereof
A controller according to the present invention has many applications. For example, it may be used to control a means for generating a force in a predetermined direction on a movable object. Thus, if the movable object is an automobile, one or more controllers may be provided to permit the following control arrangements:
(i) The derivation of the differential of acceleration in a direction transverse to the automobile may be obtained for controlling the steering of the automobile. Thus, transverse movement (lateral skidding) of the automobile may be detected, and a suitable steering compensation applied.
(ii) The differential of acceleration in a direction longitudinal to the automobile may be detected, for controlling the braking system. Thus, when an automobile is braking, a sudden change in deceleration corresponds to skidding and this may be detected using the differential of acceleration and the braking system controlled to release the wheels, which may be locked in such a skid.
(iii) In a similar way, by detecting the differential of acceleration in a direction longitudinal to the automobile, it is possible to detect whether the wheels of the automobile are skidding due to excess power, with the automobile motor then being controlled so that the wheels again maintain a firm grip.
(iv) By detecting the differential of acceleration in the vertical direction, it is then possible to control an active suspension of the automobile, so as to provide a ride which is more smooth.
Furthermore, in an automobile, mounting devices may be provided for mounting the vehicle engine in the chassis, and the present invention permits those mounting devices to be controlled in dependence on the differential of acceleration of the engine, thereby to smooth the transmission of power from the engine. In particular, such an arrangement can detect mis-firing of the engine.
The present invention may also be applied to an elevator system, in which movement of the elevator cage is detected and the differential of acceleration thereof obtained. Then, the drive to the elevator may be controlled to smooth that movement, thereby reducing passenger discomfort.
Other applications of the present invention include earthquake simulators, railway systems, magnetic levitation vehicle systems, aviation systems, building vibration reduction systems, robotic (manipulator) systems, and systems for moving a platen in a predetermined plane (XY-stage systems).